Nr 27-98 - Paris, 27 July 1998

SOHO spacecraft located with ground-based radar

Ground-based radio telescopes have been able to detect the Solar and Heliospheric Observatory (SOHO) spacecraft and have found it slowly rotating near its original position in space, a potentially important step toward possible recovery of direct communications with the spacecraft.

Radio contact with SOHO, a joint mission of the European Space Agency (ESA) and NASA, was interrupted on June 25 (see ESA press release N°23-98 of 26 June 1998), an event under review by a joint ESA/NASA investigation board. (see ESA press releases N° 24 and 26-98 of 30 June and 16 July 1998).

With the encouragement of Dr. Alan Kiplinger of the National Oceanic and Atmospheric Administration's Space Environment Center in Boulder (USA), researchers at the U.S. National Astronomy and Ionosphere Center (NAIC) in Arecibo, Puerto Rico, used the facility's 305-meter diameter radio telescope to transmit a signal toward SOHO on July 23. The 70-meter dish of NASA's Deep Space Network in Goldstone (USA), acted as a receiver, locating the spacecraft's echo and tracking it using radar techniques for more than an hour.

Preliminary analysis of the radar data, which is ongoing, indicates that SOHO is still in its nominal halo orbit near the so-called "L-1" Lagrangian point in space, and is turning slowly at a rate of roughly one revolution per minute. Staff members of NAIC and the Deep Space Network, in close cooperation with ESA and NASA, are continuing to analyze the radar data to extract more precise information on SOHO's location and motion, which in turn could help in future recovery efforts, as SOHO's solar panels turn toward the Sun.

ESA and NASA engineers also are continuing their efforts to re-establish radio data communication with the spacecraft, encouraged by the radar measurement of a slow spin rate, which suggests minimal structural damage has occurred.

The NAIC team was led by Dr. Donald Campbell. The NAIC is operated by Cornell University, Ithaca (USA), under a cooperative agreement with the U.S. National Science Foundation, Washington. The Deep Space Network is managed by NASA's Jet Propulsion Laboratory, Pasadena (USA).

More information on SOHO, including mission status reports, is available on the Internet at or via the new ESA science website:

For further information, please contact:

ESA Public Relations Division: Tel:+33(0) Fax:+33(0)

Dr. Bernhard Fleck, SOHO Project Scientist, ESA Space Science Department, Tel:+1.301.286.4098, e-mail

Public Relations Offices